This invention relates to a variable displacement vane pump arranged to supply a hydraulic fluid to a power steering apparatus and so on for a vehicle.
Japanese Patent Application Publication No. 2007-138876 discloses a conventional variable displacement vane pump employed to a power steering apparatus and so on for a vehicle. This variable displacement vane pump includes a first plate member (corresponding to a pressure plate) and a second plate member (corresponding to a second housing) disposed on both sides of a cam ring in an axial direction. Each of the first plate member and the second plate member has a confronting surface which confronts the cam ring, and which is formed with a high pressure introduction groove arranged to receive the discharge pressure in the discharge port. The discharge pressure is introduced through the high pressure introduction groove to a portion between the cam ring and each of the both plate members, so as to decrease a sliding resistance at an eccentric movement of the cam ring.